Process for liquid development of electronic photography

ABSTRACT

A process for developing electrical latent images with a liquid developer containing at least a colouring agent, cyclic rubber and low molecular polyethylene which promote the transferring and fixing of images, and a charge controller which controls the charge of toner, all existing in an electrically insulating liquid medium which process is applicable to the electronic photography and comprises steps of visualizing electrical latent images with the liquid developer and transferring the visualized images to a transfer material.

Eniteell States Patent 1191 Malri et all.

[ PROCESS FOR LTQUllD DEVELOPMENT OE ELECTRONIC PHOTOGRAPHY [75] Inventors: Isamu Maid; Masashi lKiuehi, both of Tokyo, Japan [73] Assignee: Canon Kabushiki Kaislia, Tokyo,

Japan [22] Filed: July 19, 1972 [21] Appl. No.: 273,167

[30] Foreign Application Priority Data July 24, 1971 Japan 46-55463 July 24, 1971 Japan.... 46-55464 July 30, 1971 Japan 46-57305 July 30, 1971 Japan 46-57306 [52] 1.1.5. El. 96/1 LY, 117/37 L, 252/621 [51] Int. Cl G03g 13/10 [58] Field of Search 96/1 LY; 117/37 L; 252/621 [56] References Cited UNITED STATES PATENTS 3,041,168 6/1962 Wielicki 252/621 Dec. 10, 1974 3,079,272 2/1963 Greig 96/1 LY 3,444,083 5/1969 Oliphant 252/621 3,640,863 2/1972 Okuno 6161... 252/621 3,676,121 7/1972 Jones 117/37 LE Primary ExaminerDavid Klein Assistant Examiner-John L. Goodrow Attorney, Agent, or Firm-Toren, McGeady and Stanger [57] ABSTRACT A process for developing electrical latent images with a liquid developer containing at least a colouring agent, cyclic rubber and low molecular polyethylene which promote the transferring and fixing of images, and a charge controller which controls the charge of toner, all existing in an electrically insulating liquid medium which process is applicable to the electronic photography and comprises steps of visualizing electrical latent images with the liquid developer and trans ferring the visualized images to a transfer material.

8 Claims, 5 Drawing Figures PMENTEB DEC 1 0 i974 Fae. 5

FIG.

BACKGROUNDS OF THE INVENTION 1. Field of the Invention The present invention relates to a process for liquid development of electronic photography suitable to the electronic photography, which comprises steps of visualizing electrical latent images on a surface with a liquid developing agent for electronic photography and then transferring the developed images to a transfer material.

2. Description of the Prior Art So many kinds of electronic photography have been known in which electrical latent images formed by many different processes were developed with liquid developers to obtain visualized images. Such processes of electronic photography have also been known that consisted of visualizing electrical latent images on a surface with liquid developers for electronic photography and transferring the visualized images to a transfer material.

For example, Japanese Patent Publication Sho 45-24077 describes a process for electronic photography in which electrostatic images are formed on the surface of an insulating layer of a photosensitive material composed of electroconductive base plate, photoelectroconductive layer and an insulating layer as basic components.

The liquid developers to be used in the processes in which electrical latent images formed on an insulating layer or a photosensitive layer are developed with a liquid developer and developed images are transferred to a transfer material are required to have following properties: the said electrical latent images are developed into clear fogless images; any force applied to the developed images does not disturb to obtain clear images transferred; the developed images should produce sufficiently clear transferred images on a transfer material; and finally the transferred images are firmly fixed to the transfer material.

Liquid developers so far used for electronic photography are to develop electrostatic latent images formed on electronic photographic paper mostly of zinc oxidebinder mixture. On examining these commercial liquid developers for electronic photography for the purpose to transfer a developed image to a transfer material, the developers were found to have any of the following difficulties: l) the developed images were so poorly transferred that, even if sufficiently clear images were produced on the photosensitive or insulating layer, the transferred images were of low density and bad quality, (2) transferred images were fixed very poorly to the transfer material and lightly rubbing with a finger when the carrier liquid of the liquid developer was dried up made the images so blurred as to make practical use of these developers impossible.

The present invention can be applied to an electronic photography which have completely solved the above problems, and provides a process for liquid development of electronic photography using a liquid developer which permits images of good quality, excellent property in being transferred and sufficient fixing of the transferred images to be obtained.

SUMMARY OF THE INVENTION The present invention relates to a process for developing electrical latent images with a liquid developer containing at least a colouring agent and cyclic rubber in an electrically insulating liquid, which is applicable to the electrical photography comprising processes of visualizing electrical latent images formed on an insulating or a photoelectroconductive layer with a liquid I developer and of then transferring the developed images to a transfer material.

The present invention relates to a process for developing electrical latent images developer containing at least a colouring agent and cyclic rubber in an electrically insulating liquid, which is applicable to the electronic photography comprising processes of uniformly charging the surface of insulating layer of a photosensitive body that is composed of supporting material, photoelectroconductive layer and insulating layer as basic constituents, of obtaining electrical latent images by irradiating an original figure under the simultaneous corona discharge followed by uniformly exposing to light the whole surface of the photosensitive body, of visualizing the latent images with a liquid developer and of transferring the images to a transfer material.

The present invention relates to a process for developing electrical latent images with a liquid developer containing in an electrically insulating liquid at least a colouring agent and cyclic rubber as an accelerating agent of transferring images in a liquid developing process which is applicable to the electronic photography comprising processes of uniformly charging the surface of insulating layer of a photosensitive body that is composed of supporting material, photoelectroconductive layer and insulating layer as basic constituents, of obtaining electrical latent images by irradiating an original figure under the simultaneous corona discharge followed by uniformly exposing to light the whole surface of the photosensitive body, of visualizing the latent images with a liquid developer and of transferring the images to a transfer material, while the process employs a liquid developing apparatus for electrostatic latent images which is provided with a storage tank for the liquid developer, photosensitive body, developing electrode where the said liquid developer could be pooled at a very short distance from the photosensitive body placed thereabove, a distributor of the said liquid developer by which the liquid developer could be distributed from the said storage tank through the central part of the developing electrode to every part of the same, buffering material for the stream of liquid developer which serves to prevent a rapid flow of the developer from coming into direct contact with the photosensitive body, and a circulating device for the said liquid developer by which the developer is recovered from the said developing electrode into the storage tank via a recovering dish and then supplied to the distributor.

The present invention relates to a process for developing electrical latent images with a liquid developer containing in an electrically insulating liquid at least a colouring agent, cyclic rubber and low-molecular polyethylene, which is applicable to the electronic photog raphy comprising processes of visualizing electrical latent images formed on an insulating or a photoelectroconductive layer with a liquid developer and transferring the images to a transfer material.

The present invention relates to a process for developing electrical latent images with a liquid developer containing in an electrically insulating liquid at least a coluring agent, cyclic rubber which serves to accelerate fixing and transfer properties of the images and low molecular polyethylene (having molecular weight 1,000 to 5,000), which is applicable to the electronic photography comprising processes of uniformly charging the surface of insulating layer of a photosensitive body that is composed of supporting material, photoelectroconductive layer and insulating layer as basic constituents, of obtaining electrical latent images by irradiating an original figure under the simultaneous corona discharge followed by uniformly exposing to light the whole surface of the photosensitive body, of visualizing the latent images with a liquid developer and of transferring the images to a transfer material.

The present invention relates to a process for developing electrical latent images with a liquid developer containing in an electrically insulating liquid at least a colouring agent, cyclic rubber which serves to accelerate fixing and transfer properties of the images and low molecular polyethylene (having molecular weight 1,000 to 5,000) in a liquid developing process which is applicable to the electronic photography comprising processes of uniformly charging the surface of insulating layer of a photosensitive body that is composed of supporting material, photoelectroconductive layer and insulating layer as basic constituents, of obtaining electrical latent images by irradiating an original figure under the simultaneous corona discharge followed by uniformly exposing to light the whole surface of the photosensitive body, of visualizing the latent images with a liquid developer and of transferring the images to a transfer material, while the process employs a liquid developing apparatus for electrostatic latent images which is provided with a storage tank for the liquid developer, photosensitive body, developing electrode where the said liquid developer could be pooled at a very short distance from the photosensitive body placed thereabove, a distribution of the said liquid developer by which the liquid developer could be distributed from the said storage tank through the central part of the developing electrode to every part of the same, buffering material for the stream of liquid developer which serves to prevent a rapid flow of the developer from coming into direct contact with the photosensitive body, and a circulating device for the said liquid developer by which the developer is recovered from the said developing electrode into the storage tank via a recovering dish and then supplied to the distributor.

The present invention relates to a process for developing electrical latent images with a liquid developer containing in an electrically insulating liquid at least a colouring agent, cyclic rubber, low-molecular polyethylene and lecithin, which is applicable to the electronic photography comprising processes of visualizing electrical latent images formed on an insulating or a photoelectroconductive layer with a liquid developer and of then transferring the developed images to a transfer material.

The present invention relates to a process for developing electrical latent images with a negatively charged liquid developer containing in an electrically insulating liquid at least a colouring agent, cyclic rubber and lowmolecular polyethylene (molecular weight being 1,000 to 5,000) which serve to accelerate the fixing and transfer properties of images, and lecithin as charge controller to control the charge to be applied to toner, which is applicable to the electronic photography comprising processes of uniformly charging the surface of insulating layer of a photosensitive body that is composed of supporting material, photoelectroconductive layer and insulating layer as basic constituents, of obtaining electrical latent images by irradiating an original figure under the simultaneous corona discharge followed by uniformly exposing to light the whole surface of the photosensitive body, of visualizing the latent images with a liquid developer and of transferring the images to a transfer material.

The present invention relates to a process for develrial, photoelectroconductive layer and insulating layer as basic constituents, of obtaining electrical latent images by irradiating an original figure under the simultaneous corona discharge followed by uniformly exposing to light the whole surface of the photosensitive body, of visualizing the latent images with a liquid developer and of transferring the images to a transfer material, while the process employs a liquid developing apparatus for electrical latent images which is provided with a storage tank for the liquid developer, photosensitive body, developing electrode where the said liquid developer could be pooled at a very short distance from the photosensitive body placed thereabove, a distributor of the said liquid developer by which the liquid developer could be distributed from the said storage tank through the central part of the developing electrode to every part of the same, buffering material for the stream of liquid developer which serves to prevent a rapid flow of the developer from coming into direct contact with the photosensitive body, and a circulating device for the said liquid developer by which the developer is recovered from the said developing electrode into the storage tank via a recovering dish and then supplied to the distributor.

The object of the present invention is to provide a process for liquid developing in the electronic photography using a liquid developer which, when applied to the electronic photography where electrical latent images formed on an insulating or a photoelectroconductive layer are developed and transferred to a transfer material, permits images of excellent quality, good transfer and fixing property of the images to be obtained.

The immersion development so far used in the liquid developing process is likely to be accompanied by fogging when a relatively concentrated developer is used to obtain high density images suitable to be transferred.

The present invention has solved the mentioned difficulty and provides a process for developing in the electronic photography in which use of a relatively concentrated liquid developer enables to obtain high density images of good quality, superior in the transfer prop erty and the transferred images are completely fixed.

The present inventors, through investigations of liquid developers of electronic photography applied to the transferring process of the electronic photography,

have found that a liquid developer containing in the form of dispersion in an electrically insulating liquid a colouring agent, cyclic rubber and a charge controller remarkably improves the transfer property of developed images. The actual effect will be illustrated later in examples with reference to experimental data.

The present inventors have further found that a liquid developer for electronic photography containing in an electrically insulating liquid a colouring agent, cyclic rubber and low-molecular polyethylene are superior in the transfer property and further in the fixing property. The actual effect will be discussed in the later examples referring to experimental data.

The present inventors have further found that a liquid developer for electronic photography containing in an electrically insulating liquid a colouring agent, cyclic rubber, low-molecular polyethylene and lecithin can produce high density images without forming any fogs and the images are capable of being transferred and fixed effectively. The actual effect will be discussed in in detail in later examples with particular reference to experimental data.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The composition of the liquid developer of the present invention is as follows: the developer solution contains in the dispersed form 0.2 to 6.0 g, preferably 0.5 to 2.5 g, of dyestuff or pigment, 0.2 to 6.0, preferably 1.0 to 4.0 g, of cyclic rubber, 0.1 to 3.0 g, preferably 0.2 to 2.0 g, of low-molecular polyethylene and 0.005 to 0.1 g, preferably 0.01 to 0.06 g, of lecithin per 1 liter of electrically insulating liquid as carrier liquid.

Those electrically insulating liquids and colouring agents which have been used as constituent for liquid developer of the electronic photography may be used in the present invention. Namely, aliphatic hydrocarbons, aromatic hydrocarbons and halogenated hydrocarbons having the electrical resistance larger than ohm.cm and specific dielectric constant smaller than'3 may be generally used. They include, for example, npentane, cyclohexane, isoparaffin, chlorinated paraffin, naphtha. kerosene and light oil. Any pigment and dyestuff which have been used as developer in the electronic photography may be also used in the present invention.

Furthermore, to improve the transferring and fixing property, one or more substances selected from the group consisting of phenolic, coumarone, acrylic, and alkyd resins, liquid paraffin, solid paraffin, chlorinated paraffin, chlorinated rubber, higher carboxylic acids, and metal salts thereof may be added, if necessary, to the liquid developer for the electronic photography of this invention. Especially among them, phenolic and coumarone resins remarkably improve the property.

The liquid developer for the electronic photography of this invention can be applied to the process of electronic photography in which electrical latent images formed on the surface of a photosensitive layer of zinc oxide-binder, an inorganic photoconductive layer such as of amorphous selenium, an organic photoconductive layer or an insulating layer are developed and then transferred to a transfer material, where zinc oxidebinder photosensitive paper of any kind of previous use may be used and well-known organic photoelectroconductive substances including vinylcarbazols such as poly-9-vinylcarbazol and derivatives thereof, aromatic amino derivatives such as amino-polyphenyl and pyrazolino-pyrazolines derivatives such as pyrazoline, imidalizine may be applied to this purpose. Inorganic photoelectroconductive substances which may be used in this invention include amorphous selenium, selenium-tellurium alloys and sulphides of selenium or cad mium.

The developers of this invention are also useful when electrical latent images formed on an insulating layer such as polyester films are developed and transferred.

Particularly when photosensitive materials composed of three layers, that is electroconductive supporter, photoelectroconductive layer and insulating layer, are desired, they can be prepared by finely dispersing N- type photoelectroconductive microcrystals, such as cadmium sulphide and zinc oxide, in binders, such as expoxy resin, acrylic resin, vinyl chloride-vinyl acetate copolymer and polyvinyl chloride, and applying on a metal base plate such aluminum, zinc and copper; or otherwise, by applying organic photoelectroconductive substances, such as poly-N-vinylcarbazol, chlorinated poly-N-vinyl-carbazol, in a 5 to p. dry thickness and either placing on the layer an insulating film, for example, made of polyester film or further applying an insulating resin layer, for example, of epoxyresin. The mentioned photosensitive materials composed of the three layers, that is supporter, photoelectroconductive substance and insulating layer, are described in detail in Japanese Patent Publications Sho 42-23910 and Sho 43-24748.

An example of a process of the electronic photography in which a photosensitive material composed of above three layers is as follows: at first the surface of the insulating layer of photosensitive material composed of three layers is uniformly charged by a corona discharge at +5 to 8 KV, and is irradiated by the original images under the simultaneous application of the ac. corona discharge at 5 to 8 IQV followed by uniformly exposing to light to form electrostatic latent images on the surface of the photosensitive material, and is then developed with the above liquid developer containing a colouring agent, cyclic rubber, low-molecular polyethylene and lecithin dispersed in an electrically insulating liquid, and the corona discharge at -5 to 7 KV is applied to the surface of the images formed to limit the charged electricity and finally, after an excessive amount of the liquid developer is removed, a transfer paper is applied to the images with the corona dis charge at +5 to 8 1(V from the opposite side of the paper, then clear figures can be obtained on the transfer paper when the paper is removed from the surface of insulating layer.

The electrically insulating liquid remaining on the transfer paper is removed by blowing with hot air on the surface to obtain completely fixed figures.

l-lereinunder, the developing apparatus employed in the present invention will be described in detail with particular reference to the attached drawings.

FIG. ll illustrates a preferred apparatus in which the developing part of this invention is incorporated;

FIGS. 2 and 3 show two different types of vessel for the liquid developer in the developing part from which the liquid developer overflows; and

FIGS. 4 and 5 show two different shapes of distributor.

In FIG. 1, the storage tank 1 contains the liquid developer 2, and the developer is maintained in a suspension by occasionally agitating with a stirrer 3. While in use, the liquid developer is transported by a pump 4 via the adjusting valve 5 to the distributor 6.

The part 7, to which the liquid developer is transported by the distributor 6, forms an interspace and the dimension is decided in consideration of the flow of the liquid developer and diameter and shape of the orifices 8 of the distributor 6 so that the direction of flow and the flow characteristics of the liquid developer can be substantially eliminated. The diameter of the orifices may be usually larger than 3.175 mm or one-eighth inch, but may be smaller in case when an exceptionally low rate of flow of the liquid developer is required.

A pool 9 of the liquid developer is formed on the said interspace 7 and side plates (10) and the upper surface of the pool is kept in contact with the surface to be developed supported on the photosensitive drum 11.

The contact area of the photosensitive material with the liquid developer may be varied by changing the interval between the side plates 10 and the photosensitive drum 11, and is furthermore controllable by adjusting the flow rate of the liquid developer. Unconsumed liquid developer overflows at the ends of side plates into the recover 13 and then transported back into the storage tank 1 through the pipe 14.

In order to decrease the directional flow characteristics in connection of the orifices 8 and the slot 15, some apparatus is provided with buffering material 16 for the liquid flow above the orifices or the slot, permitting the interspace 7 to be decreased. More particularly, the buffering material for flow serves to prevent direct flow from the orifices 8 of the distributor 6 toward the surface of photosensitive material from excessively washing and marring the images.

The developing unit, 6 and 10, may be insulated from the earth, if necessary, so that a bias voltage is applied to the side plates 10 to control developing, and the circuitry to this end is illustrated by dotted lines in the figure, where 17 is supply source of the bias voltage, and wires 18 are supply leads-to the side plates 10 and the photosensitive drum 11, and further accessories such as squeezing roller 19 which controls transportation of the carrier liquid may be installed so long as their functions do not deviate from the essential features of the present invention.

FIG. 2 shows the distributor 6 and the side plates 10 as appears in FIG. l in an equiangular projection, where both ends of the unit remain unlimited.

In FIG. 3, side boards 12 are used to increase the depth of the developer pool. Other parts are referred to above as shown by the reference numbers.

FIG. 4 is an equiangular projection of the distributor 6, particularly showing how the developer 2 passes through the orifices 8 and forms the developer pool in FIG. 1.

FIG. 5 shows a modification of the distributor 6 in which orifices are replaced by a single slot 15. In the case when this type of distributor is used, the developer is supplied to the distributor 6 at the center, at both ends, at one end or at any part as desired.

As is evident from the above description, the present developing apparatus is favoured by use of stationarily stirred liquid developer, where the toner particles are uniformly supplied and homogeneously distributed throughout the whole range of images without local depletion nor excess of density because the toner is continuously supplied in a flow pattern. Further, the flow pattern is eliminated and a uniform flow results well below the surface on which development occurs, so that the images do not come into direct contact with a stream of developer which may cause to disturb the image formation. As a result, a concentrated developer can be used to obtain high quality images without introducing fogs.

This is more clearly observed in the experimental data which will appear in later sections to show the effects of the present invention.

When the mentioned apparatus is employed, the liquid developer should preferably be more concentrated than usual ones. Thus, per 1 liter of an electrically insulating liquid as carrier, 0.5 to 6.0 g, preferably 1.0 to 3.0 g, of colouring agent such as dyestuff and pigment, 0.5 to 6.0 g, preferably 1.0 to 4.0 g, of cyclic rubber, 0.2 to 5.0 g, preferably 0.4 to 3.0 g, of low-molecular polyethylene (molecular weight being about 1,000 to 5,000) and 0.005 to 0.1 g, preferably 0.01 to 0.06 g, of lecithin should be contained in a dispersed form.

The present invention will be understood more clearly by the following examples.

EXAMPLE 1 Photoelectroconductive zinc oxide g Styrene-butadiene copolymer (50% solution 20 g in toluene) nButylmethacrylate (50% solution in toluene) 40 g Toluene g Rose Bengale (1% solution in methanol) 4 ml The above constituents were mixed for 6 hours using a porcelain ball mill. By applying the mixture onan aluminium plate of 0.05 mm thickness with a wiper bar so as to obtain a 4011. dried thickness, and by then evaporating the solvent in a hot air a photosensitive plate of zinc oxide was prepared.

On the other hand, a mixture consisting of Carbon black 4 g EX'CHC rubber (20% solution in x lene) 60 g anganese naphthenate (20% so ution in Xylene) 5 g lsopar G 120 g was dispersed for 20 hours in a porcelain ball mill. A 20 ml portion of the resulting dispersoid was added under stirring to 2 liters of isopar G to prepare the liquid developer.

The said photosensitive plate of zinc oxide was subjected to the corona discharge of 6 KV, the electrostatic latent images were formed by irradiating desired images, the latter being immersed in the above liquid developer to obtain visible images.

Immediately, a transfer paper was applied to the obtained images and pressed on the opposite side of the paper with a rolling rubber roller. When the paper was removed, good quality images could be found on the paper and almost no remainder of the images was observed on the zinc oxide'photosensitive plate.

EXAMPLE 2 In a process according to Example 1, the composition of the liquid developer was changed as follows:

Carbon black 4 g -Contmued Alkali blue toner l g Cyclic rubber (20% solution in toluene) 45 g Alkyd resin (80% solution in xylene) 2.4 g lsopar G 120 g The constituents were dispersed for 20 hours in a porcelain ball mill. A 20 ml portion of the dispersoid was added to 2 liters of lsopar G under agitation, to produce the liquid developer. Results were satisfactory as before.

EXAMPLE 3 Hundred grams of a 20 percent solution of poly-nvinyl'carbazol in benzene was prepared and 2 ml of a 1 percent ethanolic solution of Rose Bengale was added to it. The mixture was thoroughly mixed, applied to an aluminium plate of 0.05 mm thickness so as to obtain a a thick dried layer and dried with hot air to prepare a photosensitive plate.

On the other hand, following constituents were dispersed in a porcelain ball mill for hours:

Carbon black 4 g Phthalocyanine clue 0.5 g Cyclic rubber (20% solution in toluene) 36 g Coumarone resin (50% solutin in toluene) 14 g Linseed oil 2.5 g lsopar G 120 g EXAMPLE 4 In a vessel of Pyrex glass, granular selenium of 99.99 percent purity and powdery tellurium was mixed in ratio of 85 15. The mixture was melted in vacuum to obtain a selenium-tellurium alloy. This was placed in a melting boat and vacuum plated to a nickel-plated brass plate of 1 mm thickness at 2 X 10 Torr so as to obtain a 60p. thick layer. Electrostatic latent images were formed on the plate by charging it with the corona charging at +6 KV followed by irradiation with the original figures.

The liquid developer was prepared from the following constituents:

The all constituents were dispersed for 20 hours in a ball mill, and 40 ml of the resulting dispersoid was added under stirring to lsopar G. The said electrostatic latent images were developed by the liquid developer and transferred as in Example 3 to a transfer paper. The transferred images were extremely sharp-cut.

EXAMPLE 5 Electrostatic latent images were formed on the surface of a 38 polyester film by negatively applying corona discharge from a needle electrode pointing to the surface in accordance with images appearing on a Braun tube.

The electrostatic latent images were developed with a liquid developer prepared as follows:

Carbon black 4 g Cyclic rubber (20% solution in toluene) g Iron naphthenate 2.5 g Toluene 120 g Preparation of the liquid developer and transferring of the developed images to a transfer paper were conducted in the same manner as in Example 1. The transferred images obtained were very sharp-cut.

To illustrate the effect of the present invention, Comparison Examples 1 to 4 are shown below in which procedures were the same as in Examples 1 to 5 except that different developers were used, and experimental data for comparison on the transferring property are shown in Table 1.

Table 1 Density of Density of images to be transferred A-B transferred (A) images (B) Example 1 1.20 1.10 0.10 Example 2 1.40 1.15 0.25 Comparison Example 1 1.00 0.40 0.60

Example 3 1.00 0.95 0.05 Comparison Example 2 0.95 0.40 0.55

Example 4 1.40 1.30 0.10 Comparison Example 3 1.20 0.65 055 Example 5 0.85 0.80 0.05 Comparison Example 4 0.80 0.45 0.35

In the Comparison Example 1, the liquid developer was prepared in the same manner as in Example 2 from the following constituents:

Carbon black 4 g Alkali blue toner 1 g Alkyd resin solution in toluene) 4.8 g lsopar G 180 g Development and transferring were performed in the same manner as in Example 1 using the developer.

In the Comparison Example 2, a mixture consisting of Carbon black 4 g Phthalocyanin blue 0.5 g Coumarone resin 32 g Linseed oil 7 2.5 g lsopar G g was treated as in Example 3 to prepare the liquid developer and therewith development and transferring were conducted in the same manner as in Example 3.

it In the Comparison Example 3, the liquid developer was prepared from the following constituents as in Example 4,

Acylated ligroin 2 g Carbon black 2 g Chlorinated paraffin (40% Chlorine content) 2.5 g Phenolic resin (50% solution in toluene) 17 g lsopar G 120 g and the same process as in Example 4 was followed.

The Comparison Example 4 employed the same developer as used in the Comparison Example 1 and the procedure was the same as in Example 5.

As is readily seen from the above experimental data,

the images obtained by developing with the liquid developers used in Examples 1 to 5 which contained cyclic rubber exhibited excellent property in transferring to a transfer material.

Following examples are to illustrate the effect of cyclic rubber and low-molecular polyethylene.

EXAMPLE 6 Zinc oxide 100 g Styrene-butadiene copolymcr (50% solution in toluene) g n-Butylmethacrylate (50% solution in toluene) 40 g Toluene 120 g Rose Bengale (1% solution in methanol) 4 ml Carbon black 4 g Cyclic rubber (20% solution in toluene) 60 g Low-molecular polyethylene (average molecular weight about l500) (40% solution in xylene) 15 g Alkyd resin (80% solution in xylene) 2.4 g lsopar G 120 g and a 20 ml portion of the resulting dispersoid was added under stirring to 2 liters of lsopar G to prepare the liquid developer.

Subsequently, the said photosensitive plate of zinc oxide was subjected to the corona discharge at 6 KV and thereupon electrostatic latent images were formed by irradiating original images. The plate was immersed in the said liquid developer to obtain visible images. Immediately a transfer paper was applied to the images and when the paper was removed while the paper was pressed on the opposite side with a rolling rubber roller, transferring images of good density were obtained on the transfer paper.

EXAMPLE 7 Carbon black 6 g Cyclic rubber (20% solution in xylene) 40 g Low-molecular polyethylene (average molecular weight 1000) (20% solution in xylene) 5 g Coumarone resin (20% solution in xylene) 30 g lsopar 120 g The above mixture was dispersed with a homogenizer for 10 hours. A 15 ml portion of the dispersoid was added under stirring to 2 liters of lsopar G containing 0.01 percent (by weight) of manganese naphthenate to prepare the liquid developer. Subsequently, negative electrostatic latent images formed on the zinc oxidebinder photosensitive body were developed with the said liquid developer to obtain sharp-cut images of high density. A transfer paper was applied to the images while they were still wet with the carrier liquid, and the paper was removed with an electrically grounded electroconductive rubber roller rolling on the opposite side of the paper, and thus sharp transferred images could be obtained.

The transferring property was so excellent that the density amounted to 1.5 at the highest. Fixing of the images dried by standing in the open air was complete enough to stand rubbing with a finger.

For the sake of comparison, a developing agent prepared from the same constituents of the developer of this example except polyethylene was placed in a test tube along with the developer of this example and the dispersion stability of both solutions was observed. After a week standing, no difference in dispersion was observed with naked eyes, but the microscopic observation revealed coagulation with the solution containing no polyethylene while the developer of this example remained in perfect dispesion.

In place of the polyethylene of the average molecular weight 1,000 used in this example, polyethylenes of the average molecular weight 2,000, 2,200, 3,500 and 5,000 were also used with almost similar results.

EXAMPLE 8 EXAMPLE 9 Carbon black 4 g Cyclic rubber (20% solution in toluene) 60 g Low-molecular pol eth lene (average molecular weight 1500) 40 0 solution in xylene) 15 g Boiled linseed oil 6 g lsopar G l20 g and 20 ml of this dispersoid was added to 2 liters of lsopar G under agitation to obtain the liquid developer.

Subsequently, the said photosensitive plate was submitted to the corona charging at +6 KV, electrostatic latent images were formed on it by irradiating the plate with the original figures, and then the plate was immersed in the liquid developer. Immediately after the development, a transfer paper was applied to the images and the paper was removed while being treated against the surface, the discharge being performed in accordance with original figures appearing on a Braun tube. The electrostatic latent images were developed with the liquid developer prepared from the following with the corona charging a 7 KV from the opposite 5 Components: side. Tranferred images of good quality was obtained by th1s procedure. Carbon a 207 i l 52 g Cyclic ru er r so ution in xy ene) g EXAMPLE 10 Low molecu2la1bgolyth lenle (average lmolecular 20 wei ht Onsoutioninx ene) g Granular selemllm 9- p F P y p y 10 Coumar ne resin (20% solution in xylene) 30 g tellurlum were m1xed in a who of 85 to 15 1n a Pyrex lsopar G 120 g glass vessel and fused in vacuum to prepare a telluriumselenium alloy. This was transferred to a fusion boat and was plated on a nickel-plated brass plate of 1 mm thickness by vacuum p1ating under a vacuum 2 X 15 A mlxture conslstmg of above constituents was mixed Torr to obtain 60p. thick layer. The photosensitive thoroughly a hom?gem,zer hours and a plate thus formed was subjected to the corona charging poftlon of h resultmg dlsperlsold. W added under at +6 KV followed by irradiation with original figures agltatlon to 2 mars oflsopar G comammg to Obtain electrostatic latent images bydzeighlt of manganese naphtheriate to prepare the liq- The li uid develo er used was re ared as follows: ul eve Oper' q p p p The above electrostatlc latent 1mages were developed with the liquid developer and transferred as in Ex- Carbon black 4 g ample 6. The sharpness of the tranferred figures was Cyclic rubber (20% solution in xylene) 60 g e ll t Lowmolecular polyelhylene ,Y:: g For the purposes to illustrate the effect of this inven- Bitumen (saturated solution in lsopar G) 150 g tion comparative data are shown in Table 2.

"" 7 Table 2 Photo- Density of image sensitive matenal Before After After transtrans- (A)(B) fixing (B )-(C ferring ferring test (A) (B) Example 6 L05 L00 0.05 0.95 0.05 do. 7 L00 0.90 0.l0 0.80 0.10 Comparison ZnO-binder Example 4 0.90 0.80 0.10 0.45 0.35 do. 5 0.85 0.25 0.60 do. 6 1.00 0.90 0.10 0.50 0.40 do. 7 1.10 0.45 0.65 0.20 0.25 Example 9 1.20 l.l0 0.10 1.05 0.05

Poly-N- Comparison vinyl- Example 8 carbazol 1.30 1.10 0 20 0.60 0.50 do. 9 1.00 0.45 0 0.25 030 Example 10 L40 L25 L20 0.05

Selenium- Comparison Tellurium Example 10 1.25 1.15 0.10 0.75 0.40

do. 11 1.00 0.40 0.60 Example ll 0. 80 0.05., 0.80 0.00

Direct Comparison discharge Example 12 to film 0.90 0.80 0.10 0.40 0.40

(Density of images was measured with a reflexion densitometer.)

EXAMPLE I 1 Electrostatic latent images were formed by the negative corona discharge conducted directly on the surface of a 38p. polyester film with a needle electrode placed Comparison Examples 4 to 12 were carried out as follows:

COMPARISON EXAMPLE 4 Carbon black 4 C clic rubber (20% solution in toluene) 60 g kyd resin solution in xylene) 2.4 g

lsopar G g A mixture consisting of above components was treated in the same manner as in Example 6 to prepare a liquid developer and transferred images were obtained as in Example 6. a

COMPARISON EXAMPLE Carbon black 4 g Alkyd resin (80% solution in xylene) 4.8 g 5 Isopar G 120 g A liquid developer was prepared from the above components in the same manner as in Example 6 and transferred images were obtained as in Example 6.

COMPARISON EXAMPLE 6 Carbon black 6 a Cyclic rubber (20% solution in xylene) 40 g Coumarone resin solution in xylene) g Isopar G l20 g From above materials as components a liquid developer was prepared in the same manner as in Example 7 and transferred images were obtained as in Example 7.

COMPARISON EXAMPLE 7 25 Carbon black 6 g Coumarone resin (20%solution in xylene) 55 g Isopar G 120 g A liquid developer was prepared from the above materials as components and transferred images were produced as in Example 7.

COMPARISON EXAMPLE 8 Carbon black 4 g Cyclic rubber (20% solution in toluene) 60 g Boiled linseed oil 6 g Isopar G I20 g A mixture consisting of the above components was treated in the same manner as in Example 9 to prepare a liquid developer and using this developer transferred images were obtained as in Example 9.

A liquid developer was prepared from the above constituents in the same manner as in Example 9 and using this developer transferred images were obtained as in Example 9.

COMPARISON EXAMPLE 10 Carbon black 4 g Cyclic rubber (20% solution in xylene) g 60 Bitumen (saturated solution in lsopar G) I50 g A liquid developer was prepared from the above materials in the same manner as in Example 10 and using this developer transferred images were obtained as in Example 10.

COMPARISON EXAMPLE 1 l A mixture consisting of above materials was used to prepare a liquid developer in the same manner as in Example IO and using this developer transferred images were obtained as in Example 10.

COMPARISON EXAMPLE 12 Carbon black 6 g Cyclic rubber (20% solution in xylene) 55 g Coumaronc resin (20% solution in xylene) 30 g lsopar G I20 g A liquid developer was prepared from the above components in the same manner as in Example 1 l and transferred images were obtained as in Example 11 using the said developer.

The test for fixing was carried out as follows: five sheets of soft paper were fixed at an end, 6 mm X 10 mm, of a metal bar and the bar was placed with the said end in contact with the transferred figures. The bar was moved 5 times in the horizontal direction while kept in touch with the figures. The pressure during the process was controlled to be 12 g/cm Density of the images was measured before and after the treatment with a reflection densitometer and the fixing property was defined by the decrease in the value of the density.

Examples in which cyclic rubber, low-molecular polyethylene and lecithin were contained are illustrated below.

EXAMPLE 12 Zinc oxide g Styrene-butadiene copolymer (50% solution in toluene) 20 g n-Butyl methacrylate (50% solution in toluene) 40 g Toluene g Rose Bengale l% solution in methanol) 4 ml A mixture consisting of above components was mixed thoroughly with a porcelain ball mill for 6 hours. This was applied to an aluminium plate of 0.05 mm thickness with a wire bar so as to obtain a 40p. thick layer when dried, and by evaporating the solvent by hot air a photosensitive plate of zinc oxide-binder system was prepared. The resulting photosensitive material was treated by the corona discharge at -6 KV to charge the whole surface uniformly and then electrostatic latent images were formed on it by irradiating with original figures.

On the other hand, following components were dispersed for 20 hours with a porcelain ball mill:

Carbon black 4 g Cyclic rubber (20% solution in toluene) 60 g Low-molecular polyethylene (average molecular 15 g weight 1500) (40% solution in xylene) cithin 0.01 g Isopar G 120 g Immediately, a transfere paper was placed on the obtained images and it ws removed slowly while being pressed with a rolling rubber roller from the opposite side. Thus, transferred images of good quality was obtained on the transfer paper.

EXAMPLE 13 One hundred grams of a 20 percent solution of poly- N-vinyl-carbazol in benzene was prepared and stirred to homogenuity with 2 ml of a 1 percent solution of Carbon black 4 g Cyclic rubber (20% solution in toluene) 60 g Low-molecular polyethylene (average molecular g weight 1500) Lecithin 0.01 g lsopar G 120 g was thoroughly mixed and dispersed with a porcelain ball mill for hours. A 20 ml portion of this dispersoid was added to 2 liters of lsopar under stirring to prepare the liquid developer. Using this developer, the above electrostatic latent images were developed to obtain sharp figures on the surface of the photosensitive material. Immediately after the development, a transfer paper was placed on the surface and the paper was removed while being submitted to the corona chargingat 7 KV from the opposite side. Transferred images of good quality were obtained.

EXAMPLE l4 Granular selenium of 99.99 percent purity and powdery tellurium were mixed in the ratio of 85 to 15 in a Pyrex glass vessel and melted in vacuum to prepare a selenium-tellurium alloy. This was transferred to a melting boat and was vacuum plated on a nickel-plated brass plate of 1 mm thickness so as to obtain a 60 .4 thick layer under 2 X 10 Torr. Electrostatic latent images were formed on this photosensitive plate by treating with the corona charging at +6 KV followed by irradiation of original figures.

On the other hand, following components were thoroughly mixed for 1 hour with a homogenizer:

Carbon black 6 g Cyclic rubber (20% solution in xylene) 40 g Low-molecular polyethylene (average molecular weight 5 g 1000) (20% solution in xylene) Coumarone resin (20% solution in xylene) g lsopar G 120 g and a 20 ml portion of the resulting dispersoid was added under stirring to 2 liters of lsopar G containing 40 ml of lecithin to prepare the liquid developer. Using this developer the above electrostatic latent images were developed and fogless sharp figures of high density were obtained. Figures transferred to a transfer paper in the same manner as in Example 13 were sharp and of very high density.

Further, almost the same results were obtained when polyethylenes of the average molecular weight 2,000, 2,200, 3,500 and 5,000 were used instead of 1,000.

EXAMPLE 15 When the amount of polyethylene in Example 14 was varied to 8, 16, 32 and 45 percent by weight of the total solid components, the dispersibility was observed to be more improved with the increase of polyethylene. However, for 45 percent by weight of polyethylene images were of low density even with a fresh developer and the images blotted easily.

EXAMPLE l6 Electrostatic latent images were formed on the surface of a 38 x polyester film by applying directly the positive corona discharge from a needle electrode pointing to the surface in accordance with signals appearing on a Braun tube.

The electrostatic latent images were developed with the following liquid developer:

Carbon black 6 g Cyclic rubber (20% solution in xylene) g Low-molecular polyethylene (average molecular weight 20 g 200) (40% solution in xylene) Coumarone resin (20% solution in xylene) 30 g lsopar G 120 g A mixture consisting of the above components was dispersed for an hour with a homogenizer. A 15 ml portion of this dispersoid was added under agitation to 2 liters of lsopar G containing mg of lecithin to prepare the liquid developer.

The above electrostatic latent images were developed with the said liquid developer and the figures obtained were transferred in the same manner as in Example 12. The transferred figures were satisfactorily sharp.

To illustrate the effect of this invention, data for the comparison experiments are shown in Table 3.

Table 3 Density Densit Densit Densit Photoof of y of y of y sensitive image image (A)( B) fogging image (B)-(C) material Before er After transfer transfer fixing (B) Example 12 ZnO- 1.00 0.95 0.05 0.06 0.90 0.05

binder Comparison system 1 Example 13 0.80 0.70 0.05 0.08 0.65 0.05 do. 14 0.65 0.25 0.40 0.10 0.20 0.05 Example 13 Poly-N- 1.20 1.10 0.10 0.02 1.00 0.10

Table 3 -Continued P Denfsity Dengity Denfs ity Density hotoo 0 of sensitive image image (A)-( B) fogging image (B )(C) material Before After After transfer transfer fixing (A) (B) Comparison carbazol Example 0.85 0.80 0.05 0.05 0.75 0.05 do. 16 0.80 0.40 '0.40 0.15 0.30 0.10 Example 14 Selenium- 1.25 1.15 0.10 0.01 1.05 0.10

tellurium Comparison Example 17 0.90 0.80 0.10 0.08 0.70 0.10 do. 18 0.90 0.45 0.45 0.12 0.20 0.25 Example 15 Direct 0.80 0.75 0.05 .02 0.70 0.05

discharge Comparison to the Example 19 film 0.60 0.50 0.10 0.06 0.45 0.05 do. 20 0.60 0.25 0.35 0.10 0.20 0.05

(Density of images was measured with a rellcxion densitometer.) I

Comparison Examples .13 through 20 were con- COMPARISON EXAMPLE 18 ducted as follows:

COMPARISON EXAMPLE 13 Carbon black 6 g Coumarone resin (20% solution in xylene) 60 g A liquid developer was prepared in accordance with polyethylmethacrylate (20% Solution in Example 12, wherein lecithin was replaced by 0.1 g of I xylene) 40 g boiled linseed oil and using this developer transferred g;%' 128 E figures were obtained in the same manner as in Exam ple 12. 3O

COMPARISON EXAMPLE 14 Carbon black Linseed oil denatured alkyd resin (50'7r solution in xylene) 8. g lsopar G 100 g A mixture consisting of the above components was dispersed in the same manner as in Example 12 to prepare the liquid developer. Using this developer, transferred figures were obtained as in Example 12.

COMPARISON EXAMPLE 15 COMPARISON EXAMPLE 16 Carbon black Hydrogenated rosin Ethylcellulose (50% solution in toluene) Safflower oil Isopar G A mixture consisting of above components was dispersed in the same manner as in Example 13 to prepare a liquid developer. Using this developer, transferred figures were obtained as in Example 13.

COMPARISON EXAMPLE 1? A liquid developer was prepared in accordance with Example 14, wherein lecithin was replaced by 100 mg of linseed oil, and transferred figures were obtained as in Example 14.

A mixture consisting of above components was dispersed in the same manner as in Example 14 to prepare a liquid developer. Using this developer, the same procedure as in Example 14 was followed.

COMPARISON EXAMPLE 19 A liquid developer was prepared in accordance with Example 16, wherein lecithin was replaced by 200 mg of linseed oil, and other procedures were the same as in Example 16.

COMPARISON EXAMPLE 20 Carbon black 6 g Coumarone resin (20% solution in xylene) 60 g Polyethylmethacrylate (20% solution in xylene) 30 g Linseed oil 06 g Isopar G g A mixture consisting of above components was dispersed in the same manner as in Example 16 to prepare the liquid developer. Using this developer, transferred figures were obtained as in Example 16. Further, tests for the fixing property were carried out in the same way as before.

EXAMPLE 17 Cyclic rubber 3 g Low-molecular polyethylene 2 g Carbon black 2 g Xylene 30 g was dispersed and kneaded for 12 hours with a ball mill, and then dispersed in a solution of 40 mg of lecithin in 1 liter of an electrically insulating liquid (commercial name, lsopar G) with a homogenizer to obtain a liquid developer. Using this developer, the said elec trostatic latent images were developed and sharp figures were produced on the surface of photosensitive material.

The visible figures on the photosensitive surface were subjected to the corona charging at 6 KV to squeeze excessive lsopar G. A transfer paper was applied to the surface and removed from it while the corona charging at +6 KV was being applied on the opposite side. Thus, the images on the photosensitive surface were mostly transferred to the transfer paper.

Then fixed figures were produced by exposing the transferred figures to hot air and evaporating the re maining lsopar G. The density of the transferred figures, as measured with a reflection densitometer, was found at most L4. The transferred figures were not erased even by rubbing with a finger. showing perfect fixation.

EXAMPLE l8 Coumarone resin Cyclic rubber Low-molecular polyethylene Carbon black Solvesso 100 3 l A mixture of the above components was thoroughly dispersed and kneaded for 12 hours with a ball mill and then dispersed in a solution of 60 mg of lecithin in 1 liter .of an electrically insulating liquid (commercial name, lsopar G) with a homogenizer to obtain a liquid developer. Using this developer and following the procedure as in Example 17, excellent transferred figures could be obtained.

EXAMPLE l9 Phenolic resin 1.5 g Cyclic rubber 3 g Low-molecular polyethylene 1.5 g Carbon black 1.5 g Solvesso 100 g The above described ingredients were thoroughly dispersed and kneaded for 12 hours with a ball mill, and then dispersed in a solution of 40 mg lecithin in 1 liter of an electrically insulating liquid (commercial name, lsopar-G) with a homogenizer to prepare a liquid developer. Using this developer, excellent transferred figures could be obtained in the same manner as in Example 17.

EXAMPLE 2O Coumarone resin l.0 g Acrylic resin 0.3 g Cyclic rubber 1.2 g Low-molecular polyethylene (commercial name.

AC polyethylene 6) 0.4 g Carbon black 0.5 g Metal-containing dyestuff (Zapon fast blue) 0.2 g Solvesso 30 g A mixture of above components was thoroughly dispersed and kneaded for 12 hours with a ball mill and the resulting dispersoid was added to a solution of 10 mg of lecithin in 1 liter of lsopar-H under agitating with a homogenizer to obtain a liquid developer. Using this developer and following the procedure as in Example 17, excellent transferred figures could be obtained.

Table 4 below shows comparative data of density of transferred figures, results of fixation test and the transfer efficiency of this invention which are exhibited in Example 17 through 20 relative to the comparison examples where the same procedure as in Example 17 was followed except using the particular liquid developers specified for individual examples.

Liquid developers for comparison:

Comparison example 21 Carbon black 1.5 g Linseed oil denatured alkyd resin 3 g Lecithin 40 mg Comparison example 22 Carbon black 2 g Cyclic rubber 5 g Lecithin 40 mg Comparison example 23 Carbon black 2 g Cyclic rubber 3 g Acrylic resin 2 g Lec thin 40 mg Comparison example 24 Carbon black 2 g Low-molecular polyethylene 4 g Lecithin 40 mg A mixture consisting of above components was dispersed-and kneaded together with 30 g of Solvesso 100 for 12 hours with a ball mill, and then dispersed in 1 liter of lsopar with a homogenizer to obtain the liquid developer.

The developer in the comparison Example 25 was prepared in accordance with Example 17, wherein lecithin was replaced by linseed oil, and. in Comparison Example 26 the same developer as in Example 17 except that lecithin was eliminated was employed.

(Efficiency of transfer) lablc 4 Density of image Efficiency of 65 After transfer transfer fixation pager test Example 17 1.40 1.35 0.05 90 do. 18 1.30 1.25 0.05 85 do. 19 1.45 1.35 0.10 90 do. 20 1.20 1.15 0.05 80 Comparison examp 21 0.60 0.45 0.15 40 do. 22 1.05 0.60 0.40 80 do. 23 1.20 0.75 0.45 80 do. 24 0.80 0.70 0.10 55 do. 25 0.85 0.80 0.05 80 do. 26 0.35 0.30 0.05 85 Commercial developer A 0.75 0.30 0.45 60 do. B 0.40 0.20 0.20 35 Density of images was measured with a reflection densitometer.

The fixation test was carried out as mentioned before.

The efficiency of transfer was estimated as follows: the density of images on the transfer paper as well as of images peeled with a pressure-sensitive adhesive tape from the images remaining on the photosensitive surface was measured with a reflection densitometer, and therefrom the efficiency of transfer was calculated according to following formula:

reflection density of image on transfer paper reflection density of images on transfer paper reflection density of images remaining on photosensitive surface Example 21 A mixture dispersoid consisting of 100 g microcrystalline cadmium sulfide, g of a 50 percent toluene solution of vinyl chloride-vinyl acetate copolymer and 80 g of toluene was applied to an aluminum foil of 0.05 mm thickness so as to obtain a 40p thick layer when dried. A 38pthick film of polyester was adhered to it with an epoxy resin adhesive agent which is hardened at room temperature to obtain a triple layer photosensitive material. Subsequently, the insulating surface of the photosensitive material was uniformly charged by the corona discharge at +7 KV, exposed to the original figures accompanied by the ac corona discharge at 7 KV followed by exposing the whole surface to light to form electrostatic latent images.

Then a liquid developer was prepared by dispersing and kneading a mixture consisting of Cyclic rubber 3 g Low-molecular polyethylene 2.5 g Carbon hlack 3.0 g Xylene 30 g for 12 hours with a ball mill, and then dispersing in a solution of 50 mg of lecithin in 1 liter of an electrically insulating liquid (commercial name, lsopar G) with a homogenizer. Using this developer and the developing apparatus shown in FIG. 1, the said electrostatic latent images were developed and sharp figures were produced on the surface of photosensitive material.

The visible figures on the photosensitive surface were subjected to the corona charging at 6 KV to squeeze excessive Isopar G. A transfer paper was applied to the surface and removed from it while the corona charging at +6 KV was being applied on the opposite side. Thus, the images on the photosensitive surface were mostly transferred to the transfer paper.

Then, fixed figures were produced by exposing the transferred figures to hot air and evaporating the remaining Isopar G. The density of the transferred figures, as measured with a reflection densitometer, was found at most 1.4. The transferred figures were not erased even by rubbing with a finger, showing perfect fixation.

oughly mixed and kneaded for 12 hours with a ball mill, and then dispersed in 1 liter of Isopar H (trade name) containing in it mg of lecithin with a homogenizer to obtain a liquid developer. Using this developer, good transferred figures could be obtained in the same manner as in Example 21.

Example 23 Cyclic rubber 2.5 g Low-molecular polyethylene 2.0 g Coumaronc resin I 4.0 g Carbon black 1.5 g Solvessol00 30 g A mixture consisting of above components was thoroughly dispersed and kneaded with a ball mill for 12 hours, and then dispersed in l'liter of lsopar G (commercial name) containing 40 mg of lecithin with a homogenizer to obtain a liquid developer. Using this developer, transferred figures of good quality could be obtained in the same manner as in Example 21.

Example 24 Cyclic rubber 3.0 g Low-molecular polyethylene 0.8 g Phenolic resin 15 g Carbon black 1.5 g Solvesso 800 30 g A mixture consisting of above components was thoroughly dispersed and kneaded for 12 hours with a ball mill, and then dispersed in 1 liter of lsopar G (trade name) containing 20 mg of lecithin with a homogenizer to obtain a liquid developer. Using this developer, transferred figures of good quality could be obtained in the same manner as in Example 21.

To illustrate the effect of the present invention, comparative data are shown in Table 5 wherein Examples 21 through 24 and results obtained when conventional developers were used and when developing was carried out by theimmersion method are described.

In comparison Examples 27 through 30, the same procedure as in Examples 21 through 24 was followed except that developing was carried out by the immersion method.

Comparison Example 31 proceeded as in Example 21 except using the liquid developer below.

Carbon black Linseed oil denatured alkyd resin Lecithin A mixture consisting of above components was thoroughly dispersed and kneaded for 12 hours with a ball mill, together with 30 g of Solvesso 100, and then dispersed in 1 liter of lsopar G with a homogenizer to obtain a liquid developer.

Comparison Example 32 employed the same liquid developer as used in Comparison Example 31 and the immersion method of development was applied, other procedures being the same as in Example 21.

It can be concluded from Table 5 that Examples 21 through 24 of this invention provide transferred figures of good quality on a transfer paper and the fixation was also satisfactory, and, in addition, very few fogging occurred.

In contrast to above examples, good transfer property and fixation of figures were achieved in Comparison Examples 27 through 30, where, however, fogging was predominant. It may be concluded therefore that a developer of a high concentration is likely to produce fogs on figures when used by the immersion method instead of using the developing apparatus of this invention.

Since transfer property as well as fixation were very poor in comparison Examples 31 and 32, the liquid developers of this invention proved to exhibit excellent transfer and fixation properties. However, in comparison Example 31 which employed the developing apparatus of this invention, there is found less fogging.

What is claimed is:

1. In a method for developing electrical latent images wherein an electrical image is produced on a photoelectroconductive or an insulating layer, a liquid developer is applied to the layer to visualize the image, and then the visualized image is transferred to a transfer material, the improvement wherein the liquid developer comprises a coloring agent, a cyclic rubber and polyethylene having a molecular weight from about 1,000 to 5,000, said components being dispersed in an electrically insulating liquid having an electrical resistance of more than 10 ohm-cm and a specific dielectric constant of less than 3.

2. The method of claim 1 wherein the insulating liquid further contains a phenolic resin dispersed therein.

3. The method of claim 1 wherein the insulating liquid further contains a coumarone resin dispersed therein.

41. The method of claim 2 wherein the insulating liquid further contains a material selected from the group consisting of lecithin, manganese naphthenate, iron naphthenate, alkyl resin, linseed oil, chlorinated paraf- 0.2 6.0 grams of coloring agent; 0.2 6.0 grams of cyclic rubber;

0.1 5.0 grams of polyethylene; and 0.005 0.1 gram of lecithin.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent: No. 3 ,85355 4 Dated December 10. 197i! Inventor(S) ISAMU MAKI and MASASHI' KIUCHI i It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below;

In the heading of the patent, add to the recitation of the foreign priority data:

-July 30, 1971 Japan. l6573D 7.

Signed and sealed this 4th day of February 1975.

(SEAL) Attest:

McCOY GIBSON JR. 0. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PO-105O (10-69) USCOMM-DC man-P69 U.S. GOVERNMENT PRINTING OFFICE: ll! 0-3984, 

1. IN A METHOD FOR DEVELOPING ELECTRICAL LATENT IMAGES WHEREIN AN ELECTRICAL IMAGE IS PRODUCED ON A PHOTOELECTROCONDUCTIVE OR AN INSULATING LAYER, A LIQUID DEVELOPER IS APPLIED TO THE LAYER TO VISUALIZE THE IMAGE, AND THEN THE VISUALIZED IMAGE IS TRANSFERRED TO A TRANSFER MATERIAL, THE IMPROVEMENT WHEREIN THE LIQUID DEVELOPER COMPRISES A COLORING AGENT, A CYCLIC RUBBER AND POLYETHYLENE HAVING A MOLECULAR WEIGHT FROM ABOUT 1,000 TO 5,000, SAID COMPONENTS BEING DISPERSED IN AN ELECTRICALLY INSULTAING LIQUID HAVING AN ELECTRICAL RESISTANCE OF MORE THAN 10**10 OHM-CM AND A SPECIFIC DIELECTRIC CONSTANT OF LESS THAN
 3. 2. The method of claim 1 wherein the insulating liquid further contains a phenolic resin dispersed therein.
 3. The method of claim 1 wherein the insulating liquid further contains a coumarone resin dispersed therein.
 4. The method of claim 2 wherein the insulating liquid further contains a material selected from the group consisting of lecithin, manganese naphthenate, iron naphthenate, alkyl resin, linseed oil, chlorinated paraffine and bitumen.
 5. The method of claim 3 wherein the insulating liquid further contains a material selected from the group consisting of lecithin, manganese naphthenate, iron naphthenate, alkyl resin, linseed oil, chlorinated paraffine, and bitumen.
 6. The method of claim 1 wherein the insulating liquid further contains lecithin dispersed therein.
 7. The method of claim 3 wherein the insulating liquid further contains lecithin dispersed therein.
 8. The method of claim 1 wherein the liquid developer contains per liter of electrically insulating liquid: 0.2 - 6.0 grams of coloring agent; 0.2 - 6.0 grams of cyclic rubber; 0.1 - 5.0 grams of polyethylene; and 0.005 - 0.1 gram of lecithin. 